I was interviewed over the phone and wrote code in a shared Google Document. The questions weren't overly difficult, and the interviewer was excellent at guiding the direction of the code without telling me what to do explicitly.

They decided to fly me out to Mountain View, and I had four technical interviews on their campus. These were much more difficult, and I tired quickly after lunch.

If I can recommend anything, it's that you should get something to wake you up before the last two interviews. It's too easy to get tired and sloppy. Study up on those data structures and complexity analysis!